The invention concerns a shed forming device for the textile industry, comprising movable positioning elements having thread eyes for receiving threads of a material web to be produced, at least one guide element for guiding the positioning elements, a lift generating device and selectively actuable arresting devices for connecting or releasing the positioning elements to or from the lift generating device in such a way that the threads of the material web to be produced can be moved into positions which are in accordance with a pattern and a weave.
When weaving textiles threads extending in parallel (warp threads) in a weaving machine are moved in accordance with a desired pattern into an upper shed and a lower shed position respectively in order in that way to form the so-called weaving shed through which the weft thread can be guided transversely to the direction of the above-specified warp threads. After the weft thread is passed from one side of the material web to the other, the next weaving shed is produced with a different distribution of the warp threads in the upper shed and lower shed respectively, in accordance with the pattern to be woven, and the next weft thread is passed through the new weaving shed. In the simplest case one warp thread is introduced alternately into the upper shed and one warp thread into the lower shed (linen or basket weave).
The Jacquard weaving procedure is also known for the production of more complicated weaving patterns, in which the movement of the individual warp threads (hereinafter: individual threads) can be controlled in accordance with a certain program. Each individual thread for that purpose is passed through a yarn eye on a positioning element, the so-called heald, wherein the positioning element is fixed at one end to a resilient spring and at the other end to a lift element. A movement of the lift element causes a pulling force to be applied to the positioning element which thereby moves perpendicularly to the plane of the material web to be woven, causing the string to be stretched, and in so doing entrains the individual thread which passes through the thread eye. The individual threads are thus passed into the so-called upper shed. Individual threads which are passed through the yarn eye of a positioning element and to which no pulling force is applied by a lift element in contrast remain in the lower shed position. The term Jacquard machine in the narrower sense is used to designate the lift generating device in which the positioning elements can be connected to or released from a moving lift element of the lift generating device selectively, that is to say in accordance with the weaving step to be implemented in order to produce a given pattern. A Jacquard machine of that kind is generally disposed centrally and at some height above the loom as the positioning elements extending from the Jacquard machine (harness twines with healds and counter-pull springs) must be distributed over the width of the material web and in that case the hardness twines are not to involve excessively sharp angles so that excessively severe bending does not occur. The distribution of the positioning elements over the width of the material web is achieved by way of guide and arranging elements (the so-called web harness). A disadvantage with the known Jacquard weaving procedure is that, because of the described structure, it requires a considerable amount of space in terms of height and that the structural elements such as in particular the guide elements and the springs, at the high weaving speeds that the arrangement aims to achieve, are exposed to an enormous loading which results in rapid wear of those elements.
U.S. Pat. No. 3,186,439 discloses a loom in which, by means of a weaving harness-like arresting device which for the major part is mounted in front of the movable lift elements, the healds can be connected to and released from those lift elements which are movable up and down. For the purposes of reading or picking out the respective next shed position the healds, governed by the structure involved, are necessarily always moved into the middle shed after each pick. This arrangement, by virtue of the structure involved, does not afford a stationary guide and arresting device.
The object of the present invention was to provide a shed forming device for the textile industry, which is structurally simpler and more compact and which operates reliably and with a low rate of wear even at high cycle speeds.
That object is attained by a shed forming device for the textile industry, which includes movable positioning elements having thread eyes for receiving threads (warp threads) of a material web to be produced, at least one guide element for guiding the positioning elements, a lift generating device which can operate in a predetermined cycle sequence, and selectively actuable arresting devices for connecting or releasing the positioning elements to or from the lift generating device in such a way that the threads of the material web to be produced can be moved into positions which are in accordance with a pattern and a weave. The shed forming device is characterised in that at least one of the guide elements is in the form of a lift element of the lift generating device and is provided with arresting devices. The positioning elements can also be provided with arresting devices.
By virtue of a guide element being in the form of a lift element it becomes at the same time an arranging element which contributes to arranging the individual threads in a given shed. For the sake of simplicity hereinafter however reference will still only be made to guide elements. The guide elements provide for distribution and guidance of the positioning elements over the width of the material web to be produced. The consequence of at least one of those guide elements being in the form of a lift element and being provided with arresting devices is that at least a part of the positioning elements is entrained by the guide element and therefore the transmission of the lift movement is distributed over the width of the material web. Unlike the situation in the state of the art therefore the corresponding positioning elements do not need to be provided with so-called harness twines and they in turn do not need to be deflected at a comparatively sharp angle at the guide elements to a centrally arranged Jacquard machine. That has on the one hand the advantage that there are no direction-changing locations with corresponding frictional losses and wear. On the other hand the positioning elements can be of a different nature in terms of their properties. In particular they do not have to be so flexible that they permit a change in direction of that kind. That permits a greater degree of freedom in terms of the design configuration and choice of material for the positioning elements, in which respect in particular it is possible for them to be rigid to flexurally elastic, so that it is possible to omit a counter-pull spring at the opposite end of the positioning element. In that way it is possible to save on a further component which suffers from severe wear.
Preferably there are provided a plurality of guide elements which are arranged parallel and at a spacing relative to each other and which at the same time are in the form of a lift element of the lift generating device. By virtue of having a plurality of guide elements in the form of a lift element, it is possible to form more complicated sheds. Thus for example the individual threads can be set to a lower shed, a middle shed, and an upper shed, whereby it is also possible to provide for use thereof for double-plush weaving machines (three-position weaving machines).
Optionally, there is preferably provided beside the guide element or elements in the form of a lift element, at least one further guide element which can be of a stationary nature. Stationary guide elements of that kind enhance the stability and precision of the movement of the positioning elements and thus contribute to making it possible to achieve high weaving speeds in a reliable fashion and with a smooth mode of operation.
In this respect, in accordance with a development of the invention, arresting devices can be provided on the stationary guide elements, for connecting or releasing the positioning elements to or from the guide element. By virtue of those arresting devices, it is thus possible to stationarily fix the positioning elements so that they cannot participate in any movement of the lift element. The arresting devices therefore supplement corresponding arresting devices on the movable guide elements. In that respect, for a given positioning element, in a given cycle of the weaving machine, there is only ever one of the arresting devicesxe2x80x94either that on the movable guide element or that on the stationary guide elementxe2x80x94that is in the fixed condition (connection to the corresponding guide element), while the other arresting device is released. The arresting devices on the stationary guide elements cause the positioning elements to remain in the respective position when that is wanted by virtue of the patterning effect.
In accordance with. a development of the invention the guide elements have a plurality of openings which are arranged at spacings and through which the positioning elements are passed. The distribution of the positioning elements over the material web to be produced can be controlled in a simple manner, by means of the pattern of the openings.
Both the front regions, the front end regions and the end regions of the positioning elements can be such that they can be connected to or released from the guide element or elements.
In a preferred embodiment of the invention the positioning elements having the thread eyes are in the form of rigid, preferably flexurally elastic and/or preferably one-piece bodies. A rigid or fixed design configuration affords the advantage that a high degree of stability of the positioning element can be achieved in that way. That is advantageous in particular for the reason that the positioning element is exposed to a considerable loading by virtue of the high cycle sequences in weaving machines. As the present invention provides that the positioning element does not have to be of any configurations involving a change in direction, it does not have to be flexible like a twine, as in the state of the art. The positioning elements can therefore be both less expensive and also at the same time more stable and can thus be produced more reliably. In addition the flexural elasticity involved provides that the positioning element follows the movements of the lift element to which it is connected, in both directions. As a result it is possible in particular to omit a counter-pull spring at the other end of the positioning element. That not only saves on manufacturing costs but also considerably reduces the susceptibility to wear of the apparatus.
The arresting devices which are used in the shed forming device according to the invention are preferably electronically actuable in order to produce or release arresting of the positioning elements. The electronic actuatability thereof ensures that virtually any desired weaving pattern can be produced by suitable programming, in which respect a change in the pattern merely requires suitable re-programming or replacement of the software.
In addition it can be provided in accordance with the invention that the arresting devices on the guide elements and/or the stationary guide arresting elements, in the region of the openings, have recesses for the selective engagement or non-engagement of noses which are provided on the positioning elements, and that selectively actuable devices are provided for moving the positioning elements transversely with respect to the lift direction into the engagement position or the non-engagement position, and that the width of opening of the openings is such that unimpeded lift movement is possible in the non-engagement position. Alternatively it can also be provided that the positioning elements have recesses and corresponding noses are provided in the region of the openings. In that way positioning elements can be easily arrested or released respectively. The device for moving the positioning elements transversely with respect to the lift direction can be arranged stationarilyxe2x80x94in relation to the lift movementxe2x80x94and the positioning elements have completely or partially surrounding transverse displacement elements which can be actuated in a suitable manner.